As aircraft have become more technologically advanced, cockpit displays have evolved from mechanically driven gages to video display units. Modern video display units are capable of displaying many different types of information at the same time. Altitude, attitude and airspeed information were once displayed on three different instruments. Now, all three are incorporated into one display, the primary flight display (PFD). Navigational information was once derived from a compass, a radio beacon needle and a map. Now, flight path information, heading, groundspeed, wind direction, actual aircraft position and many other types of information may be displayed graphically on one display, the navigation display (ND).
The navigation display was a quantum leap in avionics technology. The navigational display allowed the pilots to have a “bird's eye view” of the flight path and aircraft position. Vertical information was incorporated into the navigational display, but it was limited. Vertical information about other traffic is shown as numbers corresponding to the number of feet above or below the aircraft altitude. Interpreting digital numbers consumes more cognitive effort that interpreting analog or graphical data, which can be important during critical phases of flight. Vertical information about terrain has also been incorporated into the navigational display. This information is also limited, however, because the elevation is given in general terms through color coding. Terrain above the aircraft altitude is shown in red. Terrain shown in red could be two thousand feet or ten thousand feet above the aircraft altitude, the pilot can not tell from looking at the display.
While the navigational display proved to be an invaluable tool for pilots, it soon became apparent that another display was needed, the vertical situation display, which could display the vertical flight path graphically just as the navigational display shows the lateral flight path graphically. Together, the navigational display and the vertical situation display give the pilot a more complete picture of the aircraft flight path and any related hazards. An example of a vertical situation display that gives basic vertical flight path information can be found in U.S. Pat. No. 6,720,891, owned by the assignee of this application, the entirety of which is hereby incorporated by reference herein.
The present invention is directed to overcoming one or more problems or disadvantages associated with the prior art.